Novel microencapsulated Pluronic–chitosan nanomicelles for lung delivery

Pluronic–chitosan micelles were subjected to spray-dryer to prepare microencapsulated nanomicelles for lung delivery using lactose as excipient. The physicochemical characterization of nanomicelles including diameter, surface charge, morphology, stability, aerodynamic diameter, and flow property were conducted. Pluronic–chitosan (Plu-Ch) micelles were prepared by changing the stirring rate and found that micelles prepared at 900 rpm have a diameter of about 408 nm, which is very suitable for further microencapsulation. Surfaces of micelle modified by chitosan carry positive charges which more readily adhere to the alveoli surface and hence increase bioavailability and enhance sustained release in the lungs. The most suitable ratios of lactose/micelles to prepare microencapsulated nanomicelles with the optimal aerodynamic diameter are 90:10 (4.22 μm) and 70:30 (4.53 μm). In vitro stability analysis indicates that once microencapsulated micelles enter the lung, they restore back to nanomicelles immediately and stay stable in the lung. The powders have good flowability and sustained drug release behavior with high release rates to maintain therapeutic concentration.